MnAl2O4

MnAl2O4 is a manganese aluminate oxide that adopts the spinel structure. It has the formula AB2O4, with Mn2+ commonly occupying tetrahedral A sites and Al3+ occupying octahedral B sites in a normal spinel arrangement, though some degree of cation disorder (inversion) can occur.

Crystal structure and composition: MnAl2O4 crystallizes in the cubic spinel structure, typically described by the space group Fd-3m. The oxide framework consists of a close-packed array of oxide ions with cations occupying interstitial tetrahedral and octahedral sites.

Synthesis and forms: It can be prepared by high-temperature solid-state reaction of MnO or MnCO3 with Al2O3 at temperatures near or above 1200 °C. Alternative routes, including sol-gel and combustion synthesis, have also been explored. The material is obtained as powders, ceramics, or single crystals, depending on the synthesis method.

Properties: MnAl2O4 exhibits high thermal stability and a high melting point as a ceramic oxide. It is largely insoluble in water and exhibits insulating behavior. The magnetic properties are influenced by Mn2+ ions and the cation distribution; at room temperature the material is typically paramagnetic, with magnetic ordering sensitive to the degree of inversion and temperature.

Applications and significance: MnAl2O4 is mainly studied as a model spinel oxide for investigating cation distribution, diffusion, and magnetic interactions in spinel materials. It has been examined for potential catalytic activity and as a functional ceramic material, though it is not widely used in large-scale industrial applications.

Safety and handling: like other inorganic oxide powders, standard laboratory safety practices apply; avoid generating and inhaling dust. No unique hazards beyond those associated with metal oxide powders.